Upper Airway Mechanics

Abstract

This review discusses the pathophysiological aspects of sleep-disordered breathing, with focus on upper airway mechanics in obstructive and central sleep apnoea, Cheyne-Stokes respiration and obesity hypoventilation syndrome. These disorders constitute the end points of a spectrum with distinct yet interrelated mechanisms that lead to substantial pathology, i.e. increased upper airway collapsibility, control of breathing instability, increased work of breathing, disturbed ventilatory system mechanics and neurohormonal changes. Concepts are changing. Although sleep apnoea is considered more and more to be an increased loop gain disorder, the central type of apnoea is now considered as an obstructive event, because it causes pharyngeal narrowing, associated with prolonged expiration. Although a unifying concept for the pathogenesis is lacking, it seems that these patients are in a vicious circle. Knowledge of common patterns of sleep-disordered breathing may help to identify these patients and guide therapy.

Complex sleep apnoea syndrome

“…Given the frequent association of central apnoea and chronic heart failure (CHF) [3], the prevalence of CHF and ischaemic heart disease (IHD) has also been studied in CompSAS. However, no consistent findings were reported [6,9,19,31].…”

“…To a lesser extent, central sleep apnoea syndrome (CSAS) can also be present, characterised by a decreased central respiratory drive during sleep, resulting in decreased or absent ventilation and disturbed gas exchange [3]. In OSAS, repetitive collapse of the upper airway takes place, which will finally lead to O 2 desaturation and arousal.…”

Anatomic Predictors of Retropalatal Mechanical Loads in Patients with Obstructive Sleep Apnea

“…To explore more effective and targeted treatments for OSA, it is important to address the primary anatomical contributors to increased mechanical loads in the retropalatal area (RP). Previous studies have shown that patients with OSA have smaller retropalatal airways, more lateral pharyngeal wall soft tissues and larger parapharyngeal fat pads than controls [4,5,6,7], implying that these anatomical features may be associated with increased airway mechanical loads. However, individuals may have varied upper airway (UA) collapsibility even if they have the same airway size, suggesting that UA mechanical loads cannot be attributed exclusively to narrowed pharyngeal cavities.…”

Avaliação da faringe de pacientes portadores de apneia obstrutiva do sono, por meio da tomografia computadorizada multislice obtida em vigília e durante o sono

“…Assim, em pacientes com SAOS, o eixo anteroposterior das VAS é maior, enquanto em indivíduos sem SAOS, é maior o eixo transversal ou, ainda, em indivíduos com SAOS, a área seccional na orofaringe se apresenta com aspecto circunferencial (19,45) . Outros possíveis fatores envolvidos na fisiopatogenia desta entidade são, ainda, citados, destacando-se o reflexo de ativação insuficiente dos músculos dilatadores das VAS nos pacientes com SAOS, durante o sono, especialmente no sono REM (46) , e o aumento da tendência colapsante das paredes faríngeas nestes pacientes (9,44) .…”

“…Mais recentemente, tem sido demonstrado que o colapso da via aérea superior ocorre durante a fase terminal da expiração, precedendo a apneia (46) .…”